1Ph.D. Candidate in Mining Eng.; Faculty of Mining Eng., Petroleum, and Geophysics; University of Shahrood

2Assistant Professor; Faculty of Mining Eng., Petroleum, and Geophysics; University of Shahrood

3Associate Professor; Faculty of Mining Eng., Petroleum, and Geophysics; University of Shahrood

4M.Sc. in Rock Mechanics; Supervisor of Zayand-Ab Consulting Engineering Company

چکیده [English]

Water flow in tunneling projects is one of the main issues that can affect the plan and activity of the tunneling. Therefore, it is necessary to predict the location and the amount of water flow into the tunnel. Past experience have shown that the accurate prediction of water flow in the excavated tunnels is not possible due to the lack of consideration all influencing factors, especially the properties and condition of joints. In this paper, in order to investigate the effect of joints properties on the water flow rate, the cross sections of Koohrang 3 from 1+897 to 1+950 km have been modeled using UDEC software. By changing the properties of joints, the flow water rate into the tunnel has been assessed. The results of this study have shown that changing the properties of joints has significant influence on the steady state water flow. Among these properties, the aperture of joint has the most significant effect on water flow rate in the tunnel.

Introduction
Analysis of water flow is necessary for construction of underground structures. In this analysis, the possibility of any kind of change in the ground water behavior and flow rate should be considered. In this paper, the effect of joints properties on the water flow rate using numerical modeling has been studied.

Methodology and Approaches
Joints properties have great influence on the water flow rate into tunnels. In order to investigate the effect of joints characteristics on the water flow rate, the cross sections of Koohrang 3 tunnel have been modeled using UDEC software. By changing the joints properties in the tunnel, the water flow rate into the tunnel has been assessed. Finally, The water flow rates obtained from the numerical modeling results has been compared with the values obtained from the analytical methods.

Results and Conclusions
The results of this study have shown that the increase of the joint spacing reduce the water flow rate into the tunnel due to the increase of size of formed blocks. In addition, increase of the joint aperture substantially increases the amount of water flow into the tunnel. Moreover, by increasing the joint orientation from 30 to 120 degrees, the maximum water flow occurs at the angle between 50 and 70 degrees. According to the results of this investigation on the joints properties, the joint aperture has the greatest effect on the water flow rate into the tunnel.

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